When to plant Black-eyed Susan in Iowa County County,
The best window to plant Black-eyed Susan in Iowa County County, is April 25–May 16, when soil warms to 50°F. Last frost typically hits April 25; first frost October 11.
When to Plant Black-eyed Susan in Iowa County, IA
This month in Iowa County, Iowa
Your Iowa County, Iowa garden is entering a new phase. Here's what's on the schedule for June and why each task matters now.
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Time to start black-eyed susan inside
Give them 6–8 weeks indoors before the last frost and you'll transplant into warm soil with seedlings that are already leaping.
Looking ahead to July
- First harvests: black-eyed susan
Rudbeckia hirta (Black-eyed Susan) is one of the most recognizable and adaptable native wildflowers in North America. Its bright golden-yellow daisy petals radiate from a dark brown central cone, providing months of color from midsummer into fall. Technically a short-lived perennial that self-seeds freely — colonies persist indefinitely in the garden — it thrives in poor soils, tolerates drought, and is irresistible to bees, butterflies, and goldfinches.
Iowa County, Iowa is in USDA Zone 5b. The average last spring frost is April 25 and the first fall frost is October 11, giving you a growing season of approximately 169 days.
At an elevation of 1,014 feet, Iowa County receives approximately 40.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 87°F, providing good warmth for Black-eyed Susan during the growing season.
Iowa County Soil Profile
Soil Type
Silt Loam
Soil pH
6.1-7.3
Drainage
Well Drained
Black-eyed Susan Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
Soil Compatibility in Iowa County
How your county's soil matches Black-eyed Susan's growing requirements.
Soil pH
Your soil pH (6.1–7.3) overlaps with Black-eyed Susan's range (6.0–7.0), though not a perfect match.
Soil Texture
The silt loam soil in Iowa County is excellent for Black-eyed Susan — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Black-eyed Susan.
Organic Matter
Organic matter is excellent (4.7%) — Black-eyed Susan will thrive.
How to Plant Black-eyed Susan
Succession Planting Black-eyed Susan
Sow every 6.9 weeks. Last sowing by Jul 23 to harvest before frost.
Black-eyed Susan Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Black-eyed Susan
Black-eyed Susan needs approximately 0.5 inches of water per week (2.2" per month). Here's how your county's rainfall compares month by month.
| Month | Black-eyed Susan Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.9" | 0" | ❄️ Dormant |
| Feb | — | 1.7" | 0" | ❄️ Dormant |
| Mar | — | 3.1" | 0" | ❄️ Dormant |
| Apr | 2.2" | 3.6" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 5" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 4.6" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 4.4" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 4.2" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 3.6" | 0" | ✅ Rainfall sufficient |
| Oct | 2.2" | 3.5" | 0" | ✅ Rainfall sufficient |
| Nov | — | 2.9" | 0" | ❄️ Dormant |
| Dec | — | 2.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Iowa County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Black-eyed Susan Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
Black-eyed Susan Planting Timeline — Iowa County, IA
Black-eyed Susan Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 21 | Feb 21 – Mar 7 |
| Transplant Outdoors | May 9 | May 9 – May 23 |
| Direct Sow | April 25 | Apr 25 – May 16 |
| Bloom | July 25 | Jul 25 – Oct 31 |
· 18" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Start Indoors |
| April | Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
60–80 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 5b
📆 Growing Season
169 days in Iowa County
Growing Tips for Black-eyed Susan in Iowa County
Direct sow Black-eyed Susan outdoors after April 25 in Iowa County when soil has warmed and frost danger has passed.
Common pests for Black-eyed Susan in this region include aphids and slugs. Use row covers early in the season and inspect plants weekly.
General growing tips
Start seeds indoors 8–10 weeks before last frost or direct-sow after last frost (needs light to germinate — press seeds onto soil surface, do not cover). Thrives in average to poor soil; rich soil causes floppy stems. Deadhead for extended bloom but leave some seed heads for winter wildlife interest and self-seeding. Although technically short-lived (3–5 years), prolific self-seeding maintains the colony. Year 2+ plants bloom most heavily. Divide every 3 years to maintain vigor.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Black-eyed Susan in Other Locations
Frequently Asked Questions
When should I plant Black-eyed Susan in Iowa County, IA?
Iowa County is in Zone 5b with an average last frost of April 25. Plan your Black-eyed Susan planting based on this frost date — see the calendar above for exact timing.
What planting zone is Iowa County, IA?
Iowa County, Iowa is in USDA Hardiness Zone 5b. The average last spring frost is April 25 and first fall frost is October 11.
When should I plant Black-eyed Susan in Iowa County County, ?
In Iowa County County, , plant Black-eyed Susan after the last frost (around April 25) and before the first frost (around October 11). Best results when soil holds above 50°F.
What growing zone is Iowa County County, for Black-eyed Susan?
Iowa County County sits in USDA Zone 5b. Black-eyed Susan grows reliably in zones 3a through 9b, so it's a good fit here.
Can Black-eyed Susan grow in Iowa County County's climate?
Yes — Black-eyed Susan grows well in Iowa County County's temperate climate. Iowa County County averages a 169-day frost-free season, with last frost around April 25 and first frost around October 11.
Your Iowa County Garden Planner — Free
A 22-page printable planner built for Iowa County (Zone 5b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.